Objectives: 1. Isolation and characterization of components involved in the mitochondrial electron transport-oxidative phosphorylation system. 2. Study of the enzymatic properties of these components in isolated form and reconstituted systems. 3. Study of the mechanistic details of energy coupling by resolution-reconstitution studies, and by photoaffinity labelling of the mitochondrial coupling sites. 4. Study of structure-function relationships and control mechanisms in mitochondria, submitochondrial particles, electron transfer complexes, and in individual enzyme components of the mitochondrial energy generation-conservation system. A recent development of major significance is the isolation of the mitochondrial energy-conserving enzyme comple. Thus, it appears that the mitochondrial oxidative phsosphorylation system is composed of 5 enzyme complexes. Complexes I, II, III and IV are concerned with electron transfer and energy generation, and complex V with energy conservation and ATP synthesis. The latter complex in the isolated state is capable of uncoupler- and oligomycin-sensitive ATP-Pi exchange (1--200 nmoles/min x mg protein at 30 degrees), is essentially devoid of respiratory chain components, but contains F1 (ATPase), the oligomycin sensitivity conferring protein, and the dicyclohexylcarbodiimide- binding protein. It also contains, in about 3-fold concentration as compared to mitochondria, the uncoupler binding component. This component is not present in the electron transfer complexes.